In the 15 years of running ThirstyBear Brewing Co. in San Francisco’s South of Market district, founder Ron Silberstein faced the prospect of losing his location and his business.

The investor group that owned the space at 661-663 Howard St. decided to sell, opening up the possibility that brewery could get kicked out of its home or see its rent spike.

Instead, Silberstein pulled together cash from investors and applied for a 504 loan backed by the U.S. Small Business Administration. He paid $5.25 million, a figure above the appraised value, for the 12,000-square-foot space that houses the brewery and popular restaurant.

“I had to bid just like anyone else; it was kind of scary for me,” Silberstein said. “The alternative is to lose your business. You have to be willing to pay a premium because it would cost so much to move.”

The deal transformed Silberstein from a tenant to an owner — a move dozens of other Bay Area businesses owners have made in the past year as real estate values have declined and interest rates remain low.

The 504 program is designed for capital expenses such as buying property or equipment, but it is most often used for real estate. Nationwide, the number of 504 loans and volume has grown steadily during the past three years to 7,983 worth $4.85 billion in 2011 from 6,609 loans worth $3.86 billion in 2009.

Those gains come after the program saw a 25 percent decline from 8,872 loans worth $5.32 billion in 2008 to 2009.

“There’s a growing awareness of the program and its benefits, which has resulted in more people taking advantage of it,” said Fernando Alvarez, who arranges 504 loans for the Bay Area office of CDC Small Business Finance, the largest SBA loan provider in California.

The top incentive for many businesses, Alvarez said, is that the loan program will lend up to 90 percent of property’s value, up to $5 million.

The option to put down 10 percent and lock in real estate costs for a lengthy period such as 20 years makes it much more feasible for businesses to buy property.

Another advantage of SBA loans are interest rates, currently at 4.83 percent. That’s lower than would be available on outside the program, but even conventional lenders are offering historically low rates.

Quality Quartz Engineering, a maker of quartz products for semiconductor, fiber optic and lighting companies, recently bought a 40,000-square-foot industrial building at 8484 Central Ave. in Newark from Catapult Properties LLC using a conventional mortgage.

“It’s an opportune time to purchase commercial properties, with prices some 30 percent off their highs,” said Todd Severson, a broker with Colliers International who represented Quality Quartz in the deal.

In some cases, the cost of a mortgage is similar to or less than rent.

For ThirstyBear, another concern was being able to stay in its SoMA location, which is within blocks of Moscone Center, the expanding San Francisco Museum of Modern Art and the new Transbay Terminal.

“I knew that the value of the property was down from what it was two to three years ago without a doubt. But I knew I was in an area that is really hot,” Silberstein said. “The truth is that in negotiating a new lease later on, I would have had to pay more no matter what.”